In motor vehicles, very strict limiting values to be observed partially apply with respect to emissions of pollutants. To observe present and in particular also future emission and/or exhaust gas limiting values, inter alia, accurate fuel metering during the injection is decisive.
However, it is to be considered that various tolerances occur during the metering. Such metering tolerances generally result from exemplar-dependent needle dynamics and exemplar-dependent static flow rates of the fuel injectors. An influence of the needle dynamics may be reduced, for example, by a mechatronic approach, for example, a so-called “controlled valve operation” (CVO). In “controlled valve operation”, activation times of the fuel injectors are adapted over the service life of a motor vehicle, for example, in the sense of a regulation. The activation signal is detected during the injection and the opening duration of the valve needle is ascertained in parallel from opening and closing point in time. The actual opening duration of each injector may thus be computed and possibly corrected.
Such a method for regulating an actual opening duration of a valve to a setpoint opening duration is discussed in DE 10 2009 002 593 A1.
Possible errors in the static flow rate result from tolerances of the injection hole geometry and the needle lift. Such errors have heretofore usually only been able to be corrected globally, i.e., with respect to all fuel injectors of the internal combustion engine jointly, for example, on the basis of a lambda regulation or mixture adaptation. However, it thus may not be recognized whether individual fuel injectors of the internal combustion engine have a deviation with respect to their static flow rate (i.e., dispense different quantities with equal opening duration), which may be relevant to exhaust gas or smooth running.
A method for dispensing quantity monitoring of an injector controller of an internal combustion engine is discussed, for example, in DE 10 2007 050 813 A1, in which a fuel quantity dispensed by the injector is monitored on the basis of a pressure drop in the high-pressure accumulator. A detailed ascertainment of causes of possible deviations and their correction is not possible in this way, however.